There are many types of apparatus, e.g., tables, chairs, etc. that are adjustable in height. This is particularly important and useful in the dramatic arts where various "props" are employed to make a scene on a stage resemble an actual location. These props normally need to be adjustable in height to fit properly into a scene with other props and with actors and actresses. In order to save time a particular prop may be height-adjustable so as to be used in different scenes. In many instances every detail of a prop need not be apparent, it being necessary only to convey the idea that a particular prop represents an actual article, e.g., a table, a chair, a desk, etc. In such instances a prop stand is convenient because it is easily movable to a desired location, and it can be covered or decorated to look like the actual article it represents. Such props are often used in a stage drama, or at a scene where moving pictures are taken or a TV camera is photographing a scene. There may, of course, be other uses for a telescopic column which can be lengthened to a desired amount and be automatically locked at that extension until unlocked. Other prior art mechanisms have required set screw arrangement to lock an extended telescopic mechanism, and similarly releasing the set screw in order to unlock the extended mechanisms. In the present invention no set screw is needed; one merely needs to extend the telescopic piece and it catches and locks in the first minute amount of release movement, although the unlocking can be accomplished by a foot pedal pressure or the like.
It is an object of the present invention to provide a locking mechanism that automatically is activated when a telescoping shaft is extended through a housing containing the locking mechanism and instantly is locked against any reverse motion; and that reverse motion is permitted when the mechanism is unlocked by pressure against a foot pedal. It is another object of the invention to provide a stand for holding a prop used in a dramatic scene, in which the prop stand is extendible in height, automatically locked, and can be unlocked by the touch of a foot on a pedal. Other objects can be understood upon reading and understanding the more detailed description of the invention which follows.